The aim of this proposal is to demonstrate that the group of physicians and scientists at the Liver Transplant Program of the University of Pennsylvania has the interest, infrastructure and resources to participate in the Living Donor Liver Transplantation (LDLT) Cohort Study among adults awaiting transplantation. Progress in the care of patients suffering from end stage liver disease has been hampered by the limited availability of donor organs for transplantation. Adult to adult LDLT is expected to significantly expand the donor pool and provide numerous organs to be transplanted into designated recipients. The initial results are encouraging, however, there are many questions related to donor and recipient outcomes and whether better management of these patients can improve these results. A prospective mutli-center study of LDLT in the adult setting is expected to: 1. Collect and analyze data that will assist in the establishment of reliable criteria for donor selection, examine operative techniques that are associated with the best short and long term outcomes, and recommend methods for long-term follow up of the donor's physical and psychosocial well being. 2. Determine recipient outcomes when compared to the cadaveric setting and study whether results are affected by preoperative selection and preparation, operative techniques, and the interrelationship between regeneration and immune response. 3. Study the effects of LDLT on clinical practice and socioeconomic issues in transplantation. Success in addressing these problems through a national collaborative network will depend on the scientific and operational performance of the centers involved in the consortium. The Penn Transplant center is committed to participate in these collaborative efforts, and contribute to the research efforts that are aimed at better understanding of medical and surgical issues of LDLT. Our proposal is divided into three sections. Section one: A description of the resources and participation of the team of physicians at Penn Transplant Center. Section two: A description and strategy for the development of a comprehensive database. Section three: Two research proposals describing a four year research effort to identify: a. the interrelationship between the regenerative process, graft function, alloimmune response, and b. the biopsychosocial impact of LDLT on donors and recipients.